Computer systems provide tools for analyzing various aspects of the world. In order to perform the analysis, virtual models are used. For example, one type of virtual model is a model describing a geological structure (i.e., a physical place). Such model is a virtual representation of the properties of the geological structure (e.g., type of rock, porosity, direction of any formations in the geological structure, and other such properties). The values of the properties may be measured or calculated.
By way of another example, a virtual model may describe mathematical relationships between properties and resulting values. Such a model may be a series of one or more mathematical equations that are used to describe the relationship. In some cases, the mathematical relationship may not be well known or may involve some estimation. In other words, the mathematical model is a heuristic. Thus, to generate such a model, one set of measured values of both the properties and the corresponding resulting values (i.e., both the properties and the resulting values are measured) are used to estimate the relationship.
Combination models may also be used. A combination model describes both the geological structure as well as the mathematical relationship between the values of various properties and the resulting value.